Personally I prefer the sets made by Kosmos? -- Senji
I don't think you're the only one, having played with a number of Germans. -- TheInquisitor
There are quite a number of "Catan games" in the series:
SettlersOfCatan is the basic game. Average game length is 10 minutes to set up and then about 40-60 minutes to play. The game's designed for 3-4 players, although /HouseRules are perfectly possible to allow 2-player versions.
Seafarers of Catan, which provides among other things lots of optional scenarios, so games can take between 30 and 120 minutes.
CitiesAndKnightsOfCatan, which adds a whole lot of complexity and playing-time to the game. It's AlexChurchill's favourite multiplayer Catan game, because of the range of different strategies or ways to acquire victory points the players can choose. Games take about 2 hours.
There are 5-6 player expansions to Settlers, Seafarers and even CitiesAndKnightsOfCatan. However, with 5-6 players, AlexChurchill finds there will always be one or two who are sufficiently far behind to be pretty sure quite early on that they're not going to win. Thus, he's of the opinion the 5-6 player games are less fun for all involved than the 3-4 player ones. It's possible the CitiesAndKnightsOfCatan 5-6 player expansion avoids this, through providing enough different options; he hasn't played it enough to be sure. Feel free to add your experiences here.
StarfarersOfCatan? is an independent game (for 3 or 4 players), not an expansion, but the connection is pretty clear. It's rather fun, if big: games take 2 hours, sometimes a little more.
There is a SettlersOfCatan/CardGame, which is designed for 2 players in the same way that the normal Catan games are designed for 3-4. It keeps a lot of concepts from Settlers while being quite a different game. It's fun and strategic, and almost always pretty close-run. Games take 1-2 hours.
There is also a 2-player StarshipCatan? card game, about which AlexChurchill knows nothing. If you can inform us, please click that link and enter some info.
Newly discovered (someone just passed me the file) is WanCatan? - Settlers, Seafarers and Cities and Knights set up to be played online. Groovy. A Google search indicates that the website is no longer in existence, but I have the .zip if anyone wants. -ChrisHowlett
Settlers Of The Stone Age is another independent game, putting the Settlers hexes on a map of the world and letting people explore outwards from Africa.
AlexChurchill: It's quite good fun. It plays quite like Starfarers. It may be prone to "an early lead grows exponentially", though, even more so than the other Settlers variants: because as players explore the world, Africa becomes desertified and produces fewer and fewer resources. Only those with settlements in the rest of the world can avoid this. Although, on the flip side, building any settlement after your fifth (and you start with three) loses you one of your earlier ones, so maybe it's not exponential.
Settlers of Nurnberg is an independent game in which you try to build up a town (Nurnberg) at the same time as building up the surrounding countryside. It uses a deck of cards to attempt to avoid the probability distortion field that occurs when Settlers is played.
Unless you have a set of computer-dice-which-enforce-the-laws-of-probability available... for example on a Nokia 9210, like AlexChurchill and Qqzm :):) See /HouseRules for a download of a Windows program to let you use this excellent idea on earlier Catan games.